Impact in Sand, Simulations and Experiments

GARD OEDEGAARDSTUEN, ANNE KATHRINE PRYTZ, JOHN F. MOXNES

Abstract

Medium caliber ammunition impacting sand has through the last years come up as an important task to study. We have studied the phenomenon by firing experiments and by numerical modelling. In this study we have evaluated the numerical modelling technique using the explicit code IMPETUS Afea. The starting point has been high speed cameras of medium caliber inert projectiles impacting sand in various oblique angles. The IMPETUS Afea code is relatively new Swedish/Norwegian code. It uses some quite new techniques as discrete particle method for modelling of sand, soil and detonating high explosives. It also uses a lagrangian node splitting technique to better handle brake-up and failure of structures. Particularly in this study, sand as discrete particles has been the focus. The discrete particle technique was initially developed for mine blast simulations, but was further developed to model sand/soil. Detonation products are modelled with a technique based on the kinetic molecular theory. Sand/soil is modelled as discrete particles that interact through penalty-based contact with damping and friction. In the firing test the projectiles were fired against a sand pool placed in a defined angle relative to the projectile line of fire direction. The sand was defined in respect of humidity and grain size distribution. To capture the impact and rebound occurrence of the projectile, high speed cameras were used. By using the IMPETUS Afea explicit numerical code, with the discrete particle method we were successfully able model the sand impact experiments with a high degree of conformity.